The invention relates to an injection molding machine having a machine frame, a stationary mold fixing plate, a movable mold fixing plate, and a cylinder plate which carries at least one piston-cylinder unit of a hydraulic or electromechanical closing mechanism. The cylinder plate on which the movable mold plate is supported and the stationary mold fixing plate are not connecting as is usual by beam members, but are connected exclusively by way of the machine frame. Under the influence of a mold closing force, the mold fixing plates which are locked together tilt slightly out of a plane extending perpendicularly to the machine frame.
Up to a few years ago, injection molding machines in which the closing force was carried by a U-shaped machine frame, without beam member preventing the frame from spreading apart, where unknown. A construction without beam members was used only in blow molding machines, which however have two movable mold fixing plates (see DE-C-20 48 258 and DE-C-23 21 694). In such a construction the mold separation plane is always disposed in the middle region of the frame and it will be clear that parallelism of the mold halves can be achieved by hingedly mounting each mold half on the associated part of the machine frame. In the case of injection molding machines however which have a stationary mold fixing plate and a movable mold fixing plate, although a publication dating from the year 1983 (see DE-A1-31 32 949) shows an arrangement without beam members, the problems which arise due to the omission of the beam members were neither mentioned nor overcome. That was first done by EP-B1-0 311 133. That publication states that, in the case of a machine of the type defined above, it is possible to control the closing forces which, in injection molding machines, are typically a hundred times greater than in blow molding apparatuses, even if only one mold fixing plate is movable. For that purpose it is necessary for the movable mold fixing plate to be arranged tiltably about a horizontal axis. In EP-B1-0 311 133, that arrangement is structurally embodied in that arranged in the piston of the piston-cylinder unit is a hinge pivot which, when the mold is closed, is in the middle region of the machine frame.